1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef _LIBCPP___FORMAT_FORMATTER_TUPLE_H
11 #define _LIBCPP___FORMAT_FORMATTER_TUPLE_H
12 
13 #include <__algorithm/ranges_copy.h>
14 #include <__chrono/statically_widen.h>
15 #include <__config>
16 #include <__format/buffer.h>
17 #include <__format/concepts.h>
18 #include <__format/format_context.h>
19 #include <__format/format_error.h>
20 #include <__format/format_parse_context.h>
21 #include <__format/formatter.h>
22 #include <__format/formatter_output.h>
23 #include <__format/parser_std_format_spec.h>
24 #include <__type_traits/remove_cvref.h>
25 #include <__utility/integer_sequence.h>
26 #include <__utility/pair.h>
27 #include <string_view>
28 #include <tuple>
29 
30 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
31 #  pragma GCC system_header
32 #endif
33 
34 _LIBCPP_BEGIN_NAMESPACE_STD
35 
36 #if _LIBCPP_STD_VER >= 23
37 
38 template <__fmt_char_type _CharT, class _Tuple, formattable<_CharT>... _Args>
39 struct _LIBCPP_TEMPLATE_VIS __formatter_tuple {
40   _LIBCPP_HIDE_FROM_ABI constexpr void set_separator(basic_string_view<_CharT> __separator) noexcept {
41     __separator_ = __separator;
42   }
43   _LIBCPP_HIDE_FROM_ABI constexpr void
44   set_brackets(basic_string_view<_CharT> __opening_bracket, basic_string_view<_CharT> __closing_bracket) noexcept {
45     __opening_bracket_ = __opening_bracket;
46     __closing_bracket_ = __closing_bracket;
47   }
48 
49   template <class _ParseContext>
50   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __ctx) {
51     auto __begin = __parser_.__parse(__ctx, __format_spec::__fields_tuple);
52 
53     auto __end = __ctx.end();
54     // Note 'n' is part of the type here
55     if (__parser_.__clear_brackets_)
56       set_brackets({}, {});
57     else if (__begin != __end && *__begin == _CharT('m')) {
58       if constexpr (sizeof...(_Args) == 2) {
59         set_separator(_LIBCPP_STATICALLY_WIDEN(_CharT, ": "));
60         set_brackets({}, {});
61         ++__begin;
62       } else
63         std::__throw_format_error("Type m requires a pair or a tuple with two elements");
64     }
65 
66     if (__begin != __end && *__begin != _CharT('}'))
67       std::__throw_format_error("The format specifier should consume the input or end with a '}'");
68 
69     __ctx.advance_to(__begin);
70 
71     // [format.tuple]/7
72     //   ... For each element e in underlying_, if e.set_debug_format()
73     //   is a valid expression, calls e.set_debug_format().
74     std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
75       auto& __formatter = std::get<_Index>(__underlying_);
76       __formatter.parse(__ctx);
77       // Unlike the range_formatter we don't guard against evil parsers. Since
78       // this format-spec never has a format-spec for the underlying type
79       // adding the test would give additional overhead.
80       std::__set_debug_format(__formatter);
81     });
82 
83     return __begin;
84   }
85 
86   template <class _FormatContext>
87   typename _FormatContext::iterator _LIBCPP_HIDE_FROM_ABI
88   format(conditional_t<(formattable<const _Args, _CharT> && ...), const _Tuple&, _Tuple&> __tuple,
89          _FormatContext& __ctx) const {
90     __format_spec::__parsed_specifications<_CharT> __specs = __parser_.__get_parsed_std_specifications(__ctx);
91 
92     if (!__specs.__has_width())
93       return __format_tuple(__tuple, __ctx);
94 
95     // The size of the buffer needed is:
96     // - open bracket characters
97     // - close bracket character
98     // - n elements where every element may have a different size
99     // - (n -1) separators
100     // The size of the element is hard to predict, knowing the type helps but
101     // it depends on the format-spec. As an initial estimate we guess 6
102     // characters.
103     // Typically both brackets are 1 character and the separator is 2
104     // characters. Which means there will be
105     //   (n - 1) * 2 + 1 + 1 = n * 2 character
106     // So estimate 8 times the range size as buffer.
107     __format::__retarget_buffer<_CharT> __buffer{8 * tuple_size_v<_Tuple>};
108     basic_format_context<typename __format::__retarget_buffer<_CharT>::__iterator, _CharT> __c{
109         __buffer.__make_output_iterator(), __ctx};
110 
111     __format_tuple(__tuple, __c);
112 
113     return __formatter::__write_string_no_precision(basic_string_view{__buffer.__view()}, __ctx.out(), __specs);
114   }
115 
116   template <class _FormatContext>
117   _LIBCPP_HIDE_FROM_ABI typename _FormatContext::iterator __format_tuple(auto&& __tuple, _FormatContext& __ctx) const {
118     __ctx.advance_to(std::ranges::copy(__opening_bracket_, __ctx.out()).out);
119 
120     std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
121       if constexpr (_Index)
122         __ctx.advance_to(std::ranges::copy(__separator_, __ctx.out()).out);
123       __ctx.advance_to(std::get<_Index>(__underlying_).format(std::get<_Index>(__tuple), __ctx));
124     });
125 
126     return std::ranges::copy(__closing_bracket_, __ctx.out()).out;
127   }
128 
129   __format_spec::__parser<_CharT> __parser_{.__alignment_ = __format_spec::__alignment::__left};
130 
131 private:
132   tuple<formatter<remove_cvref_t<_Args>, _CharT>...> __underlying_;
133   basic_string_view<_CharT> __separator_       = _LIBCPP_STATICALLY_WIDEN(_CharT, ", ");
134   basic_string_view<_CharT> __opening_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, "(");
135   basic_string_view<_CharT> __closing_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, ")");
136 };
137 
138 template <__fmt_char_type _CharT, formattable<_CharT>... _Args>
139 struct _LIBCPP_TEMPLATE_VIS formatter<pair<_Args...>, _CharT>
140     : public __formatter_tuple<_CharT, pair<_Args...>, _Args...> {};
141 
142 template <__fmt_char_type _CharT, formattable<_CharT>... _Args>
143 struct _LIBCPP_TEMPLATE_VIS formatter<tuple<_Args...>, _CharT>
144     : public __formatter_tuple<_CharT, tuple<_Args...>, _Args...> {};
145 
146 #endif //_LIBCPP_STD_VER >= 23
147 
148 _LIBCPP_END_NAMESPACE_STD
149 
150 #endif // _LIBCPP___FORMAT_FORMATTER_TUPLE_H
151